Self-locking devices for locking various structural members together and for subsequently unlocking them have been known and used for many years and there are many commercially successful self-locking devices which are currently available on the open market. However, there is always a need and desire to make these self-locking devices simpler and easier to operate, as well as more economical to manufacture and easier to maintain in use and in service. Also, there is always a need and a desire to make these self-locking devices more automatic and more self-actuating in their operation and more fool-proof and tamper-proof in their service and use.